The present invention relates to a sealing and breathing valve assembly for electric accumulators.
It is known that, inside the accumulators and during their working and/or their recharge, gases due to the electrolysis and the water evaporation contained in the electrolytic solution. This, as we know, is composed by sulfuric acid and distilled water.
A particular type of accumulators are the so-called recombined accumulators, in which the gases produced during the operation are condensed internally to the accumulator by eliminating the distilled water consumption and therefore the need to top up.
For safety reasons, the accumulator of the recombined type are provided with a set of channels made in the cover closing the case containing the elements. The elements connect the various accumulator electrolytic cells with a safety valve assembly allowing the gas breathing towards the outside when they exceed a determined pressure.
The valve assembly itself must also prevent the air from entering in the accumulator when, during the cooling, the temperature, and therefore also the pressure, decreases internally.
A sealing and breathing valve assembly for electric accumulators belonging to the known technique is represented as an example title in FIG. 1, where is indicated as a whole by A.
We can see that it comprises a substantially tubular collar B protruding from the cap C of the accumulator and communicating with the internal volume of the accumulator itself. An elastic cap is applied on the accumulator, indicated as a whole by D, composed by a tubular body E closed by a bottom F.
The cap D is also represented in the FIGS. 2 and 3, where we can see it is internally provided with three grooves G placed at 120° one among another, each one is realized by groove part of the tubular body E and also part of the bottom F.
The end of the tubular body E, in correspondence with each groove G, has a lip H adhering to the tubular collar B, in order to realize the sealing.
In case of overpressure internally to the accumulator, the gas produced is discharged from inside towards the outside through the duct I represented in FIG. 1. The duct is determined between the tubular collar B and the groove G, causing the rising of the lip H and therefore the coming out of the overpressure towards the external environment.
Vice-versa, in case of depression internally to the accumulator, the external pressure forces the lips H against the tubular collar B preventing the accumulator inlet from air entrance.
A disadvantage of the valve assembly just described is that the smallness of the grooves G, and therefore of the ducts I between the cap and the tubular collar B, make the overpressure discharge and the subsequent closing difficult, therefore rising the valve assembly inertia. The valve assembly reacts very slowly, both when the pressure internal to the accumulator increases and when decreases.
This can imply that the pressure could increase over the top values allowed.
A further disadvantage is that the sealing surface is limited only to the contact surface between the cap tubular body and the tubular collar. This is not always sufficient to guarantee the sealing against the entering in the air accumulator from the external environment, when it goes to depression.
Generally, the cited disadvantages, i.e. the great opening and closing inertia to the outside and the limited sealing towards the inside, are present, in a more or less accentuated way, in all the valve assemblies belonging to the known art, even if they are built differently from the valve assembly illustrated and described.
In order to prevent some of the disadvantages cited in the prior art, the document WO 01/82395, having the name of the applicant itself, proposes a tubular body ending with a groove neck in respect with the external surface of the breathing tube collar. The latter cooperates with the internal surface of an elastic tubular cap unmovably coupled to the outside of said tubular collar.
In such a way an annular chamber is formed between the neck and the cap, allowing the pressurized gases internal to the accumulator to push the cap tubular body radially and, at the same time, on all the circumference. This makes the gas discharge towards the external easier, and therefore reduces in some way the operation inertia of the valve assembly on the whole. This prevents dangerous pressure increases internal to the accumulator, during its use.
If, on one hand, the invention proposed by the cited document overcomes some of the cited prior art disadvantages, it is also true that some disadvantages, as the operation confidence of the valve assembly on the whole, remain.
More in particular, it is not prevented that sometimes the answer time between the cap opening and closing is longer, meaning that the cap itself is not able to breathe the gas accumulated at the same pressure level. This is because the rubber, synthetic or natural, which the cap is made of adheres to the tubular collar, where it houses creating a resistance higher than the predetermined. The adhesion comes from the chemical erosion due to the gas passage during the breathing.
In substance, the breathing valves of the known art do not guarantee an operation reliability which is substantially constant along the time.
To comply with Rule 5.1 ii of PCT, the following documents are cited as closest prior art:    SHAMBAN B: ‘BUSAK SHAMBAN: SOUPAPES A LA CARTE’ INGENIEURS DE L'AUTOMOBILE, RAIP. BOULOGNE, FR, no. 690, 1 Jun. 1994 (1994-06-01), page 15 XP000510579 ISSN: 0020-1200    EP-A-0 756 338 (HAGEN BATTERIE AG) 29 Jan. 1997 (1997-01-29)    U.S. Pat. No. 5,455,124 (SCHOLLENBERGER GERD) 3 Oct. 1995 (1995-10-03)    PATENT ABSTRACTS OF JAPAN vol. 009, no. 049 (E-300), 2 Mar. 1985 (1985-03-02) & JP 59 191260 A (NIHON DENCHI KK), 30 Oct. 1984 (1984Oct. 30).